Thursday, November 12, 2009

A quantitative ecologist looks at world history (again)   posted by Razib @ 11/12/2009 07:30:00 PM

Doing a literature search on the Price Equation for some weblog posts I found that Peter Turchin had written a new paper on world history using Price's formalism explicitly. A quantitative ecologist by training, Turchin has already written a series of books attempting to model human history in a more formal fashion than is usually the case. Though his work has a tendency to overlap with economic history, in particular cliometrics, Turchin brings a more robust theoretical toolkit from the natural sciences to the table. An ecologist once told me that the ultimate aim of his career was to "count stuff," and that professional expertise is handy when it comes mapping the distribution & abundance of the human species over time. What David Sloan Wilson is to multilevel selection theory, Peter Turchin is to "cliodynamics", his attempt to grapple with the general dynamics which characterize the cycles of human history.

Specifically, Turchin focuses the agricultural societies which mark the span between the age of the hunter-gatherers, and the industrial revolution. What I term the "traditionalist transient." Traditionalist because from our "modern" viewpoint we perceive many of the customs, institutions and values of this age as timeless and traditional. This despite the fact that they emerged in a specific and relatively brief historical transient after the Ice Age & before the Great Divergence. But this period is still important in our modern age, because the basic building blocks of contemporary identities draw from the traditionalist transient. Higher religions invariably date back to this period (Salafi Muslims and some ultra-traditionalist Roman Catholics look back to particular periods during the traditionalist transient as golden ages to be emulated), as do modern lingua francas, and the basic terms of political organization (democracy, republic, etc.). Early modern thinkers of the Enlightenment may have rejected or superseded the orthodoxies of the traditionalist transient as the Quarrel of the Ancients & Moderns was finally resolved to the satisfaction of the latter, but the context of the refutation was still to a large extent on the basis of traditionalist transient assumptions. For example, contemporary secularism, laicism and disestablishmentarianism are intelligible only in light of the fusion of the sacred and temporal which played out in the agricultural societies after the rise of Sumer. Turchin always notes that his conclusions may not, likely do not, apply to the dynamics extant in the present. But I suspect that much of what does go on in the present is intelligible only in light of the phenomena of the past. So his models are not purely abstract intellectual exercises.

Whether you think the project as a whole is worthwhile or not (see Massimo Pigliucci's skepticism), I am intrigued by the fact that Turchin focuses on Inner Asia because this is one region of the world which has long been "at the center of it all," both literally as well as more metaphorically. Some of the inferences from Turchin's framework illuminate rather well the broad observations and hints presented in Christopher Beckwith's Empires of the Silk Road. Since Beckwith is a philologist he lacks Turchin's more robust theoretical toolkit, but he naturally exhibits both more depth and granularity when it comes to the details of the history and ethnography. Setting both against each other is fascinating as one can make out binocular intellectual vision with more subtly than if just one narrative is considered.

As I said, in the paper, Warfare and the Evolution of Social Complexity: A Multilevel-Selection Approach, Peter Turchin uses the Price Equation as a theoretical framework. The reason for this is that Turchin believes that human societies within the past 10,000 years can be viewed as functional units subject to selection; in other words, they're adapting entities, organisms. The Price Equation allows one to partition variation between and within groups, variation being necessary for selection to operate upon collections of entities. Though the economist Samuel Bowles has suggested that between group genetic variance (FST) and selection (through warfare) may have values high enough in "small-scale societies" to allow for non-trivial biological group level selection, most seem to accept the contention of those who suggest that between group variance only makes cultural group selection plausibly common. Turchin is in the latter camp, in particular because his focus is not on small-scale societies, but larger polities which characterize what we would term "civilization." In the world of civilization it is clear that between group variance can be much greater culturally than biologically. Consider the example the case of Transylvanian Hungarian Protestants who could get by in late 16th century Oxford by virtue of their common fluency in Latin, combined with shared Calvinist religious precepts with many English Protestants (example from The Reformation: A History). Yet genetically Hungarians are closer to their neighbors, the Orthodox Romanians, than to the British. By intuition and impression it is clear that in relation to gene frequencies religious and linguistic identity tend to exhibit a less clinal pattern of variation. Though genes are discrete units, genetic variation approaches blending dynamics more easily than religious and linguistic variation, where pidgins and syncretisms are often marginalized or absorbed into one of the "parent" traditions.* Because languages and religions vary less gradually, it is easier for one to conceive of a clear and distinct group coherency in a selective framework. Where one entity ends and another begins is not arbitrary, the genes of France blend in to the genes of Germany more gently than do the dialects of French to those of German. It seems that selection between group genetic differences (not reducible to individual level selection) runs up against the problem of "gene flow" overwhelming divergences in frequency (I imagine in pre-modern times this gene flow consisted predominantly of the assimilation of the breeding-age women of conquered tribes). Here's an example from a primitive people:
31:9 And the children of Israel took [all] the women of Midian captives, and their little ones, and took the spoil of all their cattle, and all their flocks, and all their goods.
31:13 And Moses, and Eleazar the priest, and all the princes of the congregation, went forth to meet them without the camp.
31:14 And Moses was wroth with the officers of the host, [with] the captains over thousands, and captains over hundreds, which came from the battle.
31:15 And Moses said unto them, Have ye saved all the women alive?
31:16 Behold, these caused the children of Israel, through the counsel of Balaam, to commit trespass against the LORD in the matter of Peor, and there was a plague among the congregation of the LORD.
31:17 Now therefore kill every male among the little ones, and kill every woman that hath known man by lying with him.
31:18 But all the women children, that have not known a man by lying with him, keep alive for yourselves.

In fact, it seems likely that between group genetic differences have been driven by cultural differences. The Jews are a famous case, but this dynamic also crops up in surprising places, such as among Christian & Muslim Arabs in Lebanon. It seems likely that high FST values in small-scale societies tracks their cultural and linguistic diversity; as conventional gene flow through movement of mates between populations which can not communicate or worship different gods is likely to be dampened due to mutual unintelligibility and suspicion. By contrast, the expansive spread of the possible Y chromosomal lineage of Genghis Khan within the last 1,000 years is a testament to the power of cultural prestige and conquest over large areas to generate rapid gene flow.

The ethnogenesis of the Hazara in Afghanistan illustrate the complex interplay between religion, language and lineage. The Hazaras show clear evidence on Structure-based analyses of being an East Eurasian and West Eurasian hybrid population. Y chromosomal lineages tied to Genghis Khan the Mongols are common among them, and there are historical legends that they arose from exactly this group. Their practice of Islam & usage of a Persian dialect likely dates to the time that the Mongol Khans of the Ilkhanate accepted the religion of the local majority in the 13th century. The Mongols who refused to accept Islam emigrated to Inner Asia, while those who remained assimilated, accepting the religion and dominant language of the local populations whom they ruled. Today as a physically distinct Shia Muslim Persian speaking group in Afghanistan the Hazara are now endogamous, their biological distinctiveness a function of broader cultural-historical forces.

Of course that is just a specific concrete illustration of historical dynamics, and an atypical one at that. The general processes which Peter Turchin discusses have an extreme specific case scenario in the form of the Mongols, who left an outsized impact on the World Island. A big shift from small-scale societies to those of agricultural civilizations is the need for complex hierarchies to mediate decision making from the apex of the political pyramid. Like Archimede's lever with which he could move the world, the functional integrity of these units allowed the decisions of Genghis Khan to affect tens of millions. It is presumed that for small-scale societies primary face-to-face interaction sufficed to coordinate decision making. Interestingly, there is also compelling data which points to relative egalitarianism of material wealth to complement the flat authority structures. By the time history arises to supplement archaeology, meaning that we have records in the form of cuneiform tablets, societies are clearly already quite hierarchical (literacy probably emerged as a more sophisticated form of accounting, so rather complex economies are already necessary conditions). A reliance on rules, heuristics and institutions which coordinate and channel power tracked the crystallization of a powerful and wealthy rentier class (as well as a possible reallocation of power between the sexes). The idea that the poor will always be with us, and that true status and nobility accrue to those who can consume at leisure, as opposed to those who increase productivity, was the norm in the traditionalist transient.** Whereas in small-scale societies alien tribes were subhuman, in civilization the elites would often dehumanize their own subjects as lower orders of a different nature.

It is this last tendency which Turchin examines in this paper, to contrast it with conflicts which emerge on the "meta-ethnic frontiers." If you have read his earlier work you are familiar with the idea, which basically describes civilizational marchlands. The Muslim Ottomans, Orthodox Cossaks and Buddhist Oirats were all forged in the fires of meta-ethnic frontiers. In opposition to this is the "narcissism of small differences", whereby societies exhibit cleavage along what may otherwise seem to be marginal differences. Civil wars within polities can often by traced back to these issues, or sides aligned based on internal factions. Consider the divisions between Protestants which resulted in the English Civil War. Turchin wishes to assess the extent of ethnocide and genocide in the former vs. latter cases. Why? Because he believes that it is the former cases which are responsible for the rise of large empires and re-ordering of civilization and historical shifts. Evolutionary theory tells us that selection needs extant variation to operate, and it seems that along meta-ethnic frontiers such variation would would be extant in more copious quantities than in civilizational heartlands. In particular, along the boundaries of civilizations. Within individual societies there should be less variation, so selective forces should have less traction. To assess this he reviews the literature to evaluate the magnitude of depopulation wrought upon cities by victorious armies. This is a classic form of "hard selection".

Table 1 shows that conflict on meta-ethnic frontiers does have a stronger effect than civil wars. Why? Turchin posits a simple psychological explanation: those of different civilizational character are dehumanized, so empathy is modulated downward (it is notable that during and before the Albigensian Crusade the Cathars were subject to many conventional demonizing tropes, and effectively de-Christianized in the eyes of the rest of Christendom) .This is clear from the history of Christianity and Islam, in the medieval period the religious norms in both civilizations accepted the enslavement and maltreatment of unbelievers to an extent not acceptable for believers. This is the explanation for why some of the Christian military orders in the Baltic, whose original raison d'etre was to Christianize the native peoples, actually were among the last to allow and encourage baptism of their subjects. Baptism imposed constraints on efficient extraction of marginal product. The analogy to New World chattel slavery here is clear, as some plantation owners viewed proselytization among blacks dimly lest economics be modulated by morality. When the crossbow was invented the Roman Catholic Church attempted to ban its usage between Christian powers, though declared it acceptable as a weapon against Muslims. This sort of behavior, constraining and/or ritualizing high stakes competition and conflict within groups, while accepting a more "no holds barred" attitude toward between group conflicts is known from small-scale societies (though perhaps the contrast would manifest more in the extent of extreme barbarism with which outgroups were treated, rather than any particular norm of humanity for ingroups). Civilization simply operationalized this on a grander scale, and scaffolded human nature and channeled it through particular institutions and identities.

Peter Turchin argues, and presents data, that these frontier regions where primitive, and frankly savage, passions are channeled toward outgroups serve as the loci for new empires and mega-polities. In particular, being an ecologist, he focuses on particular ecologies as the exceptional cauldrons for state-formation: the semi-arid steppe. It is here that Turchin aligns with some of Christopher Beckwith's insights in Empires of the Silk Road. This should not be totally surprising, though we look through the glass darkly nature is fundamentally one, and history is a phenomenon rooted in nature. Beckwith attempts to generate a revisionist history of the world where the rise and fall of nomadic empires are just as salient as the ebb and flow of peasant-based civilizations, where the eruptions from the heartland echo down the centuries. And Turchin, like Beckwith, seems to hold that it is less important or relevant that the movers of history are unlettered nomads, but that they are derived from the marchlands where nomads or part-nomads are prominent on both sides of the frontier, civilized and barbarian. Consider the Cossacks who pushed the frontier of the Russian Empire back against the Tatars from the 16th to the 18th centuries. Loyal to the Russian state, Orthodox Christians, and trailblazers for Slavic culture and society, they certainly were the civilizational antithesis of the Muslim Turks descended from the Golden Horde of the Mongols. But upon closer inspection there were similarities between the Cossacks and Tatars as rough frontiersmen which exposed affinities when set against the lives of Russian peasants, or the more cultured nobility of the Russian heartland. It is known that many Tatars "went Cossack," abandoning the Muslim religion and eventually shifting toward a Slavic self-identity in the wake of defeats (though this is most notable for elite Tatars who converted to Christianity and were assimilated into the Russian noble class). This is what Turchin would label "ethnocide," cultural extermination if not physical. The men who expanded the domain of Russian civilization in the early modern era were useful barbarians (this seems especially evident to the more sophisticated and European-oriented Russian rulers of the 18th century, who relied upon and disdained & feared, the Cossack). The Turks who had crushed the first efflorescence of Slavic civilization which ran from Kiev to Novgorod were less useful barbarians. But to Turchin this distinction is not particularly important, as civilization-destroying barbarians such as the Arabs after Muhammad and the Mongols can set the stage for the emergence of a new civilizational-system (in the case of the Mongols there was of course the brief world-system of the Pax Mongolica).

So what do the data say?

If these data & the result, repackaged in a statistically significant form are any surprise to you, I recommend you read some books. The importance of the semi-arid steppe, the rise of the mounted cavalry and utility of the reflex bow are plain in the record of civilized societies. Macedonia, the Zhou & Chin, Persia the Turks are just a few examples of peoples who are barbarian or semi-barbarian, and came blazing out of the marchlands to establish a new order over civilized peoples. Naturally the horse looms large here. It is a truism that the average peasant was never more than 10 miles from where they were born. Even if the exact value on this expectation is off, the general thrust is surely correct, in the Malthusian world the average sedentarist was quite sedentary. In contrast the mounted nomads were highly mobile, with whole peoples such as the Avars migrating en masse from Mongolia to the Hungarian plain on the order of a decade! More mobile units of males operated on the scale of years, as was shown by the Turks and the Mongols whose zone of control spanned the margins of the Pacific to the Black Sea. The Mongols were simply the apotheosis of the terror and savagery which mobile calvary could inflict upon settled populations. In the classical period the Scythians and their fellow travelers ranged widely in their depredations, causing havoc in their wake. It is often forgotten that the Huns who were menacing Gaul in the 450s were strafing Syria ~400, sweeping down through the Caucasus from the plains to the north of the Black Sea. Just as the institutions of the traditionalist transient allowed for individuals at the apex of power to control and affect massive change at a distance, so the rise of the horse and bow gave the nomad a combination of mobility and lethality which was only neutralized with the spread of firearms.

Turchin dates the emergence of the nomadic warrior toolkit, and therefore the potential to wreak havoc on civilized polities, to the period between 1000-500 BCE. This sounds about right. Though the records are sparse because literate civilization was thin on the ground, this is the period when the Scythians battered the Assyrian Empire, and the Medes and Persians finally sacked Nineveh. In China the rise of this sort of nomadic lifestyle and warfare seems to have taken a bit longer, with the Xiongnu making permanent the archetype of the raw nomad beyond the frontiers of Han civilization in the 3rd century BCE. But a more critical point is that there is the suggestion that the Axial Age is a deterministic reaction on the part of civilized peoples to the hammer-blow which nomad polities dealt them (in the case of Persia you have the barbarians overwhelm, assimilate and re-order the civilizations of the Near East in totality). To Turchin this is an evolutionary process, as selection operates upon cultures and polities to give rise to adaptations to a new fitness landscape. In this case, the mounted archer, a combination of lethality and mobility which the more primitive modalities of the Bronze Age were helpless. The choice was clear, adapt or be swallowed.

To me it is notable that the Assyrians are reputed to have been particularly savage, while the Persians who were their eventual successors were depicted as relatively benevolent. Some of this is selection bias, as the Persians treated the Jews with less brutality than the Assyrians, and much of our character/narrative history of this place and period come from the Hebrew Bible. But there are other independent records of the nature of Assyrian rule, which seemed to be rather coarse and overly generous in its application of intimidation and cruelty to the conquered. From what I can tell it is as if the Assyrians were Yanomami in chariots, exhibiting a brutal inchoate savagery more the norm in small-scale societies. In contrast, the Persian system of rule were imperial, but often indirect. Local traditions were respected, but it was under the Achaemedids that the Zoroastrian religion began to develop, which later developed into a state-religion for the Persians in the manner that Christianity was for Rome and State Confucianism in China. It is likely that the ethical aspect of Judaism as an ethical monotheism came to the fore during the period of influence under the Persian Zoroastrians, whose primary deity is, Ahura Mazda, is an explicit force for good, not an angry and jealous god. In Empires of the Silk Road Christopher Beckwith suggests that the synchronous efflorescence of religio-philosophical systems across the ecumene during the Axial Age was promoted by the expansion of nomads, their ideas, and the facilitating role of their trade networks. Turchin's model would seem to suggest that nomads played a role as well, but more as antagonists for civilized polities (and in some cases the progenitors of new polities and empires), who had to increase in scale and develop institutional and ideological adaptations. The two models are not mutually exclusive. In terms of religion there are many cases of barbarians beyond the limes being influenced and innovating. Most famously with Islam, but in both Scandinavia and the Baltic before the conversion to Christianity the extant records and preserved mythologies are clear enough to show an influence and institutional mimicking of the "Roman religion." In the latter cases the cult of Baldr and the temple at Arkona were dead-ends, as Christianization eliminated those cultural experiments. A more successful universal religious model is the worship of Tengri, the sky god of the Turks and Mongols who was the focus of worship their "shamanistic" phase. The similarities of Tengri to El, one of the ancestors of the Abrahamic God, can not be a coincidence. Sky gods are portable and plainly omnipresent, looking down from on high, in a way that makes them ideal candidates for the God.

It seems that the model presented here is that from savagery comes civilization. This is basically an evolutionary model of human history, an "arms race" of ideas and institutions between polities and civilizations. Sometimes, as in the case of the mounted warrior with bow, the race was triggered by a technological change. The civilizations of the Near East, from Egypt to Mesopotamia, did not change or adapt fast enough. They became fiefs in a Persian world. It can be argued that the Classical Greeks, descendants of the barbaric city-states which sacrificed humans to placate savage gods as they were falling to the Sea Peoples, did formulate appropriate institutional (the cohesive polis and national identity) and technological (the accoutrements and organization of the hoplite phalanx) responses to the threat. In China the two dynasties which set the tone for Imperial China down to 1900, the Zhou and the Chin, emerged out of the borderlands as semi-barbarian polities. The Zhou introduced the peculiar elite Chinese variant of supernaturalism whereby worship centered around the impersonal "Heaven." The Chin state was organized around an efficient and utilitarian plan which may have been repudiated in name, but not totally in practice, by subsequent dynasties. Reorganized from within by useful barbarians China was ready to meet the nomad threat in the form of the Xiongnu.

In The Human Web: A Bird's-Eye View of World History John and William McNeill point out that history seems to have a direction in terms of human complexity. Between 1200 and 800 BCE the Greeks "forgot" how to write in totality, so that the Linear B system of the Mycenaeans has no connection to the Phoenician derived alphabet of the later period. As the ages progressed these sorts of "Dark Ages" when the clock was reset, the slate wiped clean, became less and less frequent. The world of settled humanity, dominated by rentier elites, purporting to justify their domination through transcendent truth, covered the face of the earth. Ray Haung, in China: A Macro History, observes that the interregnums between dynasties exhibits a persistent decline in length. Why? One hypothesis is that the "Chinese system," as embodied in norms and values passed down through its bureaucratic class, became more robust to the "exogenous shocks" of political chaos. Some, such as Robert Wright in Nonzero: The Logic of Human Destiny, would explain this in generally "microeconomic" terms. Game theory applied through the lens of rational actors. Turchin rejects this view insofar as he seems to be suggest that cultural units are being driven to success because of a process of expansion through the elimination of rivals. Again, there is no need to assume these are exclusive alternative choices. Religions such as Christianity and Buddhism clearly spread through individual action and choice (both seem to have been popular first among cosmopolitan urbanites, and counter-elites). But, they also clearly spread by being adopted as ideological cement for polities, the choice made on high at the apex of the political pyramid and extended down by fiat to the population as a whole. This choice may have conferred upon the polity the benefits which accrue from being members of a meta-ethnic civilizational coalition. The benefits to being members of Christendom for the pagan elites to the north of the post-Roman world were clear. James I of England asserted "No bishop, no King," to indicate the necessary connection between ruler and the priests. And so it was the arrival of Christianity seems curiously concomitant with the emergence of kings on pagan Europe, one God, one ruler. Pagan peoples who remained relatively disinclined toward joining the Christian Commonwealth were liable to be subject to ethnocide, as occurred with the Wends and the Old Prussians.

A focus on elites is evident in Turchin's model, and I think in some ways that is a critical piece of information. Group level selection on the scale that he focuses upon, large polities and such, may be a feature of only a small slice of a given polity. The elites, or particularly important military groups, such as the Cossacks. History is written by and for the elites. The gods and languages of the elites, their norms, often percolate down to the masses (though not always, my example above about a Latin speaking Transylvanian in Oxford is obviously extremely elitist, but in terms of international politics they are all who counted!). Greg Clark documented high mortality rates for the military nobility of England in Farewell to Alms, as opposed to the relative fertility of the pacific gentry. This shows how high the stakes for intergroup conflict for elites may have been, as opposed to commoners. Benjamin Franklin reputedly stated that "We must all hang together, or assuredly we shall all hang separately." Kevin Phllips reports in The Cousins' Wars that much of the Virginia planter aristocracy, including George Washington and Thomas Jefferson, were in severe debt to English financial houses. Their individual material stakes illustrate how victory or loss in war can have huge negative or positive outcomes to those at the apex of the power pyramid in agricultural societies. This is where I think the civilizational values which unite and engender a degree of cosmopolitanism among elites within the bounds of that broader meta-ethnic framework serve to dampen the savagery of loss and the gluttony of gain. The world of a defeated king may seem to collapse upon him, but if the foe shares the same civilizational presuppositions the institutions and values remain intact, and some honor and status may be retained by the rules of the game which are enforced by third parties (e.g., in medieval Europe, the Church). By contrast, it is no surprise that when the kingdom of the Visigoths fell to the armies of the Arabs and Berbers the elites either fled, or, more likely converted to Islam to preserve their positions. This was ethnocide. A process which was inverted in 1492, as Granada fell to the armies of Castile and Aragon, and the Muslim elites either had to flee to North Africa, or convert to Christianity. In the former case they lost their wealth and power. In the latter case they lost their identity. These are of course the less savage cases, on occasion elites are simply exterminated by the conquerors so that the snake's head is removed.

If Peter Turchin turns this most recent paper into a book, I have a catchy title in mind: Civilization: a tale of regicide. It has been said that science can not progress until old ideas die with old scientists, and so it may be that civilization can not proceed until old elites die prematurely thanks to the efforts of new ones. The argument is too broad to be sure, but the history of the evolution of power is a biography of the lives of those in power, so this captures much to a first approximation if it is correct.

* English has a strong influence from the Romance languages via French, but it is still recognizably a Germanic language. Similarly, Sikhism emerged as a new world religion or sect which navigated between the disjoint idea spaces which defined Hinduism and Islam, but it is notable that many Hindus claim Sikhism to be a variant of Hinduism, while no Muslims seem inclined to make this assertion.

** The poor were always with the hunter-gatherers as well, because they were all poor, but a wealthy leisured class who could comment on the plight of the poor did not exist so the observation would have been ludicrous.

Related: Historical Dynamics and contingent conditions of religion, Cliodynamics, the rise & fall of empires and asabiya.

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